Ultra high frequency vibrator



H. BENIOFF ULTRA HIGH FREQUENCY VIBRATOR Filed July 23, 1945 INVENTOR.'Huso BENIOFF Hll H N ll FIG. I

Patented Apr. 26, 1949 2,468,537 ULTRA HIGH FREQUENCY VIBRATOR HugoBeniofl, Pasadena, Calii'., assignor, by mesne assignments, to SubmarineSignal Company, Boston, Mass, a corporation of Delaware Application July23, 1945, Serial No. 606,498

' 6 Claims. (01. 25942) 1 The present invention relates to an ultra highfrequency vibrator used principally for vibrating liquids. Moreparticularly in the present inventiona small volume of liquid isvibrated within a container which is particularly adapted to fit intothe vibrator andhave an intimate acoustic coupling with the vibratingsurface.

The vibrator in the present invention maybe formed as a piezoelectriccrystal of quartz, or other suitable piezoelectric materials may be usedproducing vibrations over a uniform surface which is covered with aliquid film forming acoustic contact with a very thin membrane. Themembrane may alsobe covered with a liquid in which the container holdingthe liquid substance to be ilbrated is placed. The device is preferablyoperable at very high frequencies with comparatively high power and itmay be built in varying sizes for vibrating small test samples or largerquan ties for industrial production purposes.

"The invention will be more fully described in the specificationattached when taken in connection with the drawings showing anembodiment of the invention in which:

Fig.1 shows a plan view of the device with fragmentary portions brokenaway;

Fig.2 shows a section taken on the line 2--2 of Fig. ,3.

Fig. 3 shows a section taken'on the line 3-3 ofFig; 1;

Fig. 4 shows a detail of the piezoelectric oper--.

ating element;

Fig. 5 shows a section on the line 5-5 of Fig. 4; and

Fig. 6 shows a circuit diagram of the device of Fig. 1.

In the arrangement in Fig. 1 the unit as assembled may comprise a woodenbase I on which stands a casing or cover 2 which is preferably made ofcopper or other shielding material. A copper shield partition 3 withinthe casing 2 separates the upper part of the casing from the lower partin which the tuned power oscillating circuit is positioned. Thiscomprises a transformer 4 with an inner primary coil 5 and an outersecondary coil 6 within which is positioned a copper vane or disc 1whose position is adjusted by the external knob 8 until a maximumcurrent is indicated on the secondary current meter 9. Both the tuningdial knob 8 and the meter 9 are mounted on a metallic panel ill at thefront of the device, the panel also containing th input .plug II towhich the desired high frequency cur-' rent is conducted. Thetransformer 4 is a step up transformer so that the voltage within thedevice is at a much higher potential than that brought to the devicefrom the outside.

As indicated in Fig. 3 both primary and secondary coils may be wound oninsulating forms l2 and I3, respectively, which-may be made of plasticor other suitable material. The secondary of the coil is shunted by avacuum or mica condenser M of a very high voltage rating. This condenseris mounted on suitable insulating-supports l5 extending from the base ofthe case.

The vibrating unit itself is. shown in section in Fig. 2. This comprisesa piezoelectric crystal vibrating element 20 which has an annular groove2| in its top face and a substantial heavy ring portion 22 by means ofwhich the crystal is firmly The crystal preferably is of clamped inplace. quartz but other suitable piezoelectric material may be used.While the frequency of operation used may be considered high forcompressional wave vibration, a frequency of 500 kc. has been foundsatisfactory.

The bottom face of the crystal is coated with a conductive electrode 23of gold or other highly conductive material. The center 24 of thecrystal element preferably has a surface parallel to a thin diaphragm 25which'is positioned just above it and separated only from the top ofthe'crystal by an oil film of very little thickness. The electrode 23 onthe bottom face serves as one electrode of the system while the thindiaphragm 25, which may be of Monel metal, or the like, serves as thetop electrode acting through the oil film. The lower clamping member 26,which is recessed at the center to leave the bottom of. thepiezoelectric crystal free, except at the edges, serves as theconductive connection for the bottom electrode. This lower clampingelement is held in place by means of screws 28 inserted from the top ofan insulating supporting plate 29 of Lucite, Mycalex, or other suitablematerial. The screws 28 draw the lower clamping plate 26 tightly againstthe lower surface of the insulating plate 29 and hold the rim of thecrystal element tightly against a shoulder 3li'recessed in the sides ofthe plate adjacent the central opening 3| in the plate. An outer casing32 is attached by means of screws 33; or otherwise, to the sides of theclamping plate 26. This cover 32 is made of copper or other suitableconductive material and serves as a conductive path to the crystalelectrode through the spring contact 34 connected to the rod 35 insulated through the glass bushing 33. I serves to conduct heat away fromthe crystal. At its lower end the rod 35 connects through the conductor31 to the secondary 6 of the trans- It also former.

or diaphragm 2s. The ring as threads onto the f end of thecylindricaltube 38 and clamps, the

- diaphragm between the-fiangeof the; ring and The top. electrode",comprising the. Monelmetal thin disc, is retained in place bymeans ofmetallic sleeve 38 with an inwardly extendingflange extending overtherim of the disc providing a free release at this surface of'thecrystal in aim-gas or vacuum surroundings; The bellows, with its oilfilled chamber 4! connecting with the chamber 44, provides. forexpansion of the end of the tube. Both thering andtube are conductiveandpreferably are made ofaluminum alloy or some such similar lightconductive metal.

The cylindrical tube 38 is flared outward con ically at 40 and mergesinto a supportingstructurell which has a heavyflange ring 42" by meansof which theelement 4| is clamped tight 1y to the rim of the plasticor-Lucite element 29, making a full liquid seal. Aszwill be noted,liquid.

seals are also provided between the piezoelectric crystal element andthe top clamping shoulderil as wellas between "the Lucite element 28 andthe lower clamping ring 26.

' A liquid bellows element 42 is'attached to the.

bottom of the clamping ring 26, at its outer edge by welding, softsolder, or any other suitable method. A passage is also drilled throughthe insulatingplate 29. connecting the inside of the bellows with thechamber M formed between the f element and the insulating plate. Thischamber 44, the inside of the bellowsvand the entire surface of thecrystal element is filled with oil, i

I preferably a good insulating oil. A second chamber is formed abovethediaphragm .25 within the hollow cylinder 39 and its flared outconical ertion 40. This second chamber 45 is filled with a "liquid whichmay be, the same as the. insulatins oil in the chamber 44.

The supporting structure 4| is provided with an inwardly extendinghorizontal flange, and

also with an upwardly extending wall 41 adapted to receive a cylindricalcover it over its top and side surfaces. The inwardlyextending flange 40serves as a support for the container 48' which is provided. with ashoulder 49 adapted to rest oil produced'by heat generated in unit. Itwill also be noted that vibrational energy may be transmitted not onlythroughthe bottom of the container but also through the side walls bymeans of the liquid contact of the chamber ll.

The device herein described may be used for testing purposes by puttingsamples of the aubstances to, be tested within the container 48'.

.Ihe'se preferably should be liquid but other types or materials, suchas plastics, semi-plastics. or 15 r even solids, may be similarly testedby immersing the materials in the container. I Having now described myinvention, I claim:

l. An ultra high frequency vibrator compris ing a piezoelectric crystalhaving a rear surface and a. front-surface, a gas confining containercovering said rear surface whereby said rear surface maybe exposed to agasor vacuum medium,

said front surface covered with a liquid medium and a container inintimate contact with the liquid medium. l

2. An ultra high. frequencypiezoeiectric crys tal vibrator having aconducting electrode attached to one face of the vibrator and anotherelectrode comprisinga thin conductive membrane insulatedly mounted "withrespect to the first-mentioned electrode'n'ear the other face of the'vibratorand having onlyan oil'film between it and said otherfalce ofthe vibrator, and'acon- I tainer positioned adjacent said membrane and aagainst the flange it. The top part ofthecover I is perforated also tomake a free fltfor the container 48'. The container 48" is removable andpreferably is provided witha thin lower wall II and a thin bottomdiaphragm ll. The con-, tainer also may be covered by a cover "with oneor more vent holes 53.

The top diaphragm ",which serves as the secondelectrode, iselectricallyconnected through the supporting platefiorgstructure 4|which may begrounded to the case through a supporting second liquidmedium acting between. said'mem- .brane and said container. l l l 3. Anultra high frequency vibrator compris 'ing a piezo, electric crystalplate, a conductive electrode positioned in parallel relation to saidplate, near one face thereof, having only an oil film between theelectrode and said face of the plate, means on the other side of saidelectrode from said plate forminga liquid chamber over said electrodehaving means supporting a container and said container having the bottomthereof immersed in said liquid chamber,

4. An ultra high frequency vibrator comprising a piezoelectric crystalplate having a top surface and a bottom surface and a thin compliancerim, a gas confining containerqcovering said bottom surface whereby saidbottom surface may be exposed to a gas medium, an oil chamber formed ontop of the piezoelectric crystal plate, a conprises the transformer, theshunting condenser and the crystal oscillator. The vibrations gen!erated by the crystal oscillatorwill be transmitted through the thin oilfilm between the top. surface the short liquid pathbeneath the bottom iiof the container 48' effectively providing an acoustic coupling fortransmitting acoustic vibrations to the liquid 60 within the container40;. i

It will be noted that the lower surface or elec- 1 of the crystal andthe diaphragm 25 and through ductive electrode positioned parallel tothe piezoelectric crystal platenear said top surface and having only anoil film of said chamber between i the electrode and the plate, a secondoilchamber formed over said electrode, a container havin the substanceto be treated positioned in said second chamber over the electrode andmeans for supporting said second container in said chamber.

clamped at its edge and free around the rest of the surface of theplate, an oil chamber formed above the plate, an expandable bellowselement trode of the piezoelectric crystal is not immersed in a liquidmedium but that only the upper surface is in contact with the liquidmedium thus positioned beneath said bottom electrode and having apassageway to said; chamber, a membrane forming a thin electrodepositioned directly over the plate having an oil film between it and theplate, a second chamber formed over said membrane and a containeradapted to bcposi- 5. An ultra high frequency vibrator comprising apiezoelectric crystal plate, an electrodeat the bottom surface of saidplate, said plate being 5 tioned within said chamber, said containeradapted to contain material to be vibrated.

6. An ultra high frequency vibrator comprising a piezoelectric crystalplate having a thin compliance ring, means clamping the piezoelectriccrystal plate beyond said thin compliance ring, one of said clampingmembers comprising a large plastic non-conductive plate, the other aconductive flanged ring making electrical contact with a bottomelectrode of said plate, a liquid chamber formed over said plasticplate, a cover covering said liquid chamber, a thin membrane, meansprovided within said cover for supporting said thin membrane, said coverand membrane being of conductive material and said membrane beingparallel to said plate and sewing as an electrode therefor, a thin filmseparating said mem- 6 brane from said plate and means formed withinsaid cover comprising a second liquid chamber over said membrane and acontainer sup- P rted within said second chamber.

HUGO BENIOFF.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

